Installing and upgrading help

Would someone please tell me how to set up more than one moodle installation on the same server without loading every single moodle file to a separate set of folders? What we would like to do is that when someone goes to http://www.mydomain.com/moodle1, it brings up one configuration of moodle, but if someone goes to http://www.mydomain.com/moodle2, it brings up the same version of moodle but with an entirely different set of configuration parameters and class lists and users.  Please help.  Thanks.